A catalytic converter (colloquially, “cat” or “catcon”) is a device used to decrease the toxicity of emissions from an internal combustion engine. A catalytic converter works by using a catalyst to stimulate a chemical reaction in which toxic by-products of combustion are converted to less-toxic substances.First widely introduced on series-production automobiles in the U.S. market for the 1975 model year to comply with tightening EPA regulations on auto exhaust, catalytic converters are still most commonly used in motor vehicle exhaust systems. Catalytic converters are also used on generator sets, forklifts, mining equipment, trucks, buses, trains, airplanes and other engine-equipped machines.
The catalytic converter was invented by Eugene Houdry, a French mechanical engineer and expert in catalytic oil refining[1] who lived in the United States. Around 1950, when the results of early studies of smog in Los Angeles were published, Houdry became concerned about the role of automobile exhaust in air pollution and founded a special company, Oxy-Catalyst, to develop catalytic converters for gasoline engines – an idea ahead of its time for which he was awarded a patent (US2742437). Widespread adoption had to wait until the extremely effective anti-knock agent tetraHYPERLINK “http://en.wikipedia.org/wiki/Tetra-ethyl_lead”-HYPERLINK “http://en.wikipedia.org/wiki/Tetra-ethyl_lead”ethylHYPERLINK “http://en.wikipedia.org/wiki/Tetra-ethyl_lead” HYPERLINK “http://en.wikipedia.org/wiki/Tetra-ethyl_lead”lead was eliminated from most gasoline over environmental concerns, as the agent would “foul” the converter by forming a coating on the catalyst’s surface, effectively disabling it.[2]
The catalytic converter was further developed by JohnHYPERLINK “http://en.wikipedia.org/wiki/John_J._Mooney” J. HYPERLINK “http://en.wikipedia.org/wiki/John_J._Mooney”Mooney and CarlHYPERLINK “http://en.wikipedia.org/wiki/Carl_D._Keith” D. HYPERLINK “http://en.wikipedia.org/wiki/Carl_D._Keith”Keith at the EngelhardHYPERLINK “http://en.wikipedia.org/wiki/Engelhard_Corporation” HYPERLINK “http://en.wikipedia.org/wiki/Engelhard_Corporation”Corporation,[3] creating the first production catalytic converter .
Metal-core converter
Ceramic-core converter
The catalytic converter consists of several components:
The core, or substrate. The core is often a ceramic honeycomb in modern catalytic converters, but stainlessHYPERLINK “http://en.wikipedia.org/wiki/Stainless_steel” HYPERLINK “http://en.wikipedia.org/wiki/Stainless_steel”steel foil honeycombs are also used. The honey-comb surface increases the amount of surface area available to support the catalyst, and therefore is often called a “catalystHYPERLINK “http://en.wikipedia.org/wiki/Catalyst_support” HYPERLINK “http://en.wikipedia.org/wiki/Catalyst_support”support”. The ceramic substrate was invented by RodneyHYPERLINK “http://en.wikipedia.org/wiki/Rodney_Bagley” HYPERLINK “http://en.wikipedia.org/wiki/Rodney_Bagley”Bagley, IrwinHYPERLINK “http://en.wikipedia.org/wiki/Irwin_Lachman” HYPERLINK “http://en.wikipedia.org/wiki/Irwin_Lachman”Lachman and RonaldHYPERLINK “http://en.wikipedia.org/w/index.php?title=Ronald_Lewis_(scientist)&action=edit&redlink=1” HYPERLINK “http://en.wikipedia.org/w/index.php?title=Ronald_Lewis_(scientist)&action=edit&redlink=1″Lewis at CorningHYPERLINK “http://en.wikipedia.org/wiki/Corning_Glass” HYPERLINK “http://en.wikipedia.org/wiki/Corning_Glass”Glass, for which they were inducted into the NationalHYPERLINK “http://en.wikipedia.org/wiki/National_Inventors_Hall_of_Fame” HYPERLINK “http://en.wikipedia.org/wiki/National_Inventors_Hall_of_Fame”InventorsHYPERLINK “http://en.wikipedia.org/wiki/National_Inventors_Hall_of_Fame” HYPERLINK “http://en.wikipedia.org/wiki/National_Inventors_Hall_of_Fame”HallHYPERLINK “http://en.wikipedia.org/wiki/National_Inventors_Hall_of_Fame” of HYPERLINK “http://en.wikipedia.org/wiki/National_Inventors_Hall_of_Fame”Fame in 2002.
The washcoat. A washcoat is used to make converters more efficient, often as a mixture of silica and alumina. The washcoat, when added to the core, forms a rough, irregular surface, which has a far greater surface area than the flat core surfaces do, which then gives the converter core a larger surface area, and therefore more places for active precious metal sites. The catalyst is added to the washcoat (in suspension) before being applied to the core.
The catalyst itself is most often a precious metal. Platinum is the most active catalyst and is widely used. It is not suitable for all applications, however, because of unwanted additional reactions and/or cost. Palladium and rhodium are two other precious metals used. Platinum and rhodium are used as a reduction catalyst, while platinum and palladium are used as an oxidization catalyst. Cerium, iron, manganese and nickel are also used, although each has its own limitations. Nickel is not legal for use in the European Union (due to reaction with carbon monoxide). Copper can be used everywhere except North America, where its use is illegal due to the formation of dioxin.